For most of its length, I-93 indirectly parallels
U.S. Route 3. Particularly in
New Hampshire, the two highways have several interchanges with each other, as well as a concurrency through
Franconia Notch State Park. I-93 follows the Southeast Expressway south of downtown Boston, the
Central Artery through Boston, and the Northern Expressway from Boston to the New Hampshire state line.

Route description

Massachusetts

Interstate 93's southern terminus is at exit 12 of
I-95 in
Canton, co-signed with
U.S. Route 1 North. At this junction, I-95 North heads to the northwest (co-signed with
U.S. Route 1 South, as well as
Route 128, which begins at the interchange), to serve as the beltway around Boston, while I-95 South runs by itself southwest through Boston's southwestern suburbs toward
Rhode Island. This violates the numbering plan for the
highway system of the United States, which dictates that the signed number for odd-numbered interstates increase from west to east, and therefore I-95 should be farther east than I-93.

The southernmost 3 miles (4.8 km) of I-93 run east through Boston's southern suburbs, passing through Canton and
Randolph. In Randolph, I-93 meets the northern end of
Route 24 (Fall River Expressway/AMVETS Memorial Highway) at Exit 4. I-93 continues east into
Braintree, interchanging with
Route 3, the major freeway linking Boston to
Cape Cod, at Exit 7 (known locally as the "
Braintree Split"). Route 3 North joins I-93 and US-1, and the highway turns north toward Boston. These first 7 miles (11 km) of I-93 follows what was formerly part of
Massachusetts Route 128 before it was truncated at the current I-95/I-93 junction and many locals still refer to this section of roadway as part of Route 128.

Upon turning northward, the highway is known as the Southeast Expressway passing through
Quincy and
Milton before crossing into the city of
Boston over the
Neponset River. After the
Massachusetts Avenue connector exit, the highway officially becomes the
John F. Fitzgerald Expressway, which is also known as the
Central Artery, and passes beneath downtown Boston. A major intersection with the
Massachusetts Turnpike/Interstate 90 (Exit 20) takes place just south of downtown Boston. After the massive interchange, motorists use the
Thomas P. O'Neill Jr. Tunnel to travel underneath the city and then use
Zakim Bunker Hill Bridge to cross the
Charles River. Two exits are located in the tunnel, where the speed limit is 45 miles (72 km) an hour.
Route 3 leaves the Artery just before the Zakim bridge via Exit 26, and
U.S. Route 1 leaves the Artery just after the bridge, via Exit 27 (no southbound access). From Boston through the rest of Massachusetts,
Concord, NH appears as the control city on northbound overhead signs. The Artery ends as I-93 continues north out of the city.

I-93 continues through the northern suburbs of Boston, coming in
Woburn to a second intersection with
Interstate 95 and Route 128, which run in a concurrency. Travelers going north can either change over to I-95 north to eventually reach
Maine, or remain on I-93 toward New Hampshire. Farther north, in
Andover, I-93 meets
I-495, providing access to
Worcester to the southwest and New Hampshire's
seacoast region to the northeast. Just south of the state line, I-93 crosses the
Merrimack River into
Methuen, where it interchanges with Routes
110 and
113 at exit 46 just north of the river crossing. Prior to August 2016, the Route 110 and 113 junction beneath I-93 was a
rotary, but current construction routes the highways straight under I-93. While two new ramps are being built at the interchange to complete the new
partial cloverleaf format, there are
temporary signals and inlets at the end of two existing ramps to serve traffic that will soon be using the new loop ramps. Work began in July 2014 on the project, and with the rotary now closed, demolition of the rotary will be underway in late 2016. The full project is scheduled for completion in June 2018.[7] I-93 then interchanges with the western end of
Route 213, a connector between I-93 and I-495. I-93 then crosses into
New Hampshire after about 1 mile (1.6 km).

In all, I-93 has 48 numbered exits in Massachusetts, although several numbers are skipped in and near Boston. One noteworthy reason that some exits were removed from I-93 is to further address traffic problems in addition to converting the Central Artery from six to eight to ten lanes, by reducing the combined number of on- and off-ramps from 27 to 14.[8] Exit 48 in Methuen, just before the New Hampshire state line, is the highest-numbered exit along the entire route. I-93 once had only 22 exits prior to the re-routing of I-95 onto
MA 128.[9] Due to the highway being one of the two major Interstates that enter Boston directly (
Interstate 90 is the other), nearly the entire length of the highway in Massachusetts carries four lanes in each direction. Average daily traffic volumes on I-93 in the state range from 100,000 vehicles at the New Hampshire border[10] and 150,000 vehicles at the southern end at I-95[11] to over 200,000 vehicles through Braintree and Quincy.[10]

New Hampshire

Interstate 93 travels just over 131 miles (211 km) in the Granite State, around two-thirds of the highway's total distance. Serving as the main interstate route in New Hampshire, it connects the state capital,
Concord, and its largest city,
Manchester. Beyond Concord are the towns of
Tilton,
Plymouth, and
Littleton. I-93 is designated as the
Alan B. Shepard Highway,[12] from the Massachusetts line to
Hooksett (just north of Manchester at the northern terminus of I-293), as the
F.E. Everett Turnpike from Hooksett to Concord, and as the
Styles Bridges Highway from Concord to the Vermont line. This section of roadway was constructed between 1961 and 1977.

Between the northern end of
I-293 in Hooksett and the beginning of
I-89 in
Bow, I-93 also carries the northern end of the
Everett Turnpike. There is one toll booth along this section, at Exit 11 in Hooksett; toll for passenger cars is $1 (50¢ at the ramp toll booth). This is the only toll collected along the entire length of Interstate 93. I-93 in New Hampshire is also notable for having state liquor stores serve as rest areas, which are passed just after the toll plaza, traveling north. There are separate stores on both sides of the Interstate for travelers in each direction.

I-93 enters New Hampshire at
Salem. A rest area/welcome center is available on the northbound side of the freeway, directly before Exit 1. I-93 remains three lanes wide in each direction for its first 7 miles (11 km), until after the exit 3 interchange in Windham. It then drops to two lanes until the split with
Interstate 293 and the junction with
New Hampshire Route 101 add a third and fourth lane back to the freeway. I-93 and New Hampshire Route 101 run concurrently for about 1 mile (1.6 km) before New Hampshire Route 101 heads directly east as its own freeway, serving Portsmouth and the Seacoast region. I-93 keeps three lanes of traffic in each direction until the junction with
Interstate 89, when each side reduces back to two, and remains a four-lane freeway through most of its journey northward, with the only exception being the
Franconia Notch section.

Northbound lane of Interstate 93/US Route 3 in Franconia Notch

It crosses the
Merrimack River again before going through the state capital of
Concord. In Concord,
Interstate 393 heads directly east (co-signed with eastbound
U.S. Route 4 and
U.S. Route 202), providing another route to the Seacoast region. Westbound U.S. Route 4 joins I-93 and runs concurrently with it until Exit 17 for Penacook, about 5 miles (8.0 km) further north, before exiting westward. Continuing north, I-93 traverses the
Lake Winnipesaukee tourist region and makes its way north through the heart of the
White Mountains Region. I-93 passes through
Franconia Notch State Park as a
Super-2 parkway (one lane in each direction) with a 45 miles per hour (70 km/h) speed limit, designed to reduce I-93's impact on Franconia Notch. For the trip through Franconia Notch, I-93 and
U.S. Route 3 run concurrently.

Beyond Franconia Notch State Park, U.S. 3 heads northeastward through the
Great North Woods region, while I-93 runs to the northwest. The final town along I-93 in New Hampshire is
Littleton, served by four exits. Many motorist services are available at Exit 42. After passing through town, it crosses the
Connecticut River into
Vermont. The last exit along I-93 is exit 44 for
Monroe, through which a rest area/welcome center is accessible to travelers on both sides of the highway.

In 2013, a bill was signed by governor
Maggie Hassan to raise the speed limit on Interstate 93 to 70 mph (115 km/h) from mile marker 45 to the Vermont border. The new limit took effect on January 1, 2014.

Vermont

Interstate 93 runs for 11 miles (18 km) in
Vermont, with one numbered exit in the state before ending at the interchange with
Interstate 91 in
St. Johnsbury in the
Northeast Kingdom of Vermont. A rest area/welcome center is located along the northbound side of the highway for travelers entering from New Hampshire. The final 3 miles (4.8 km) of the Interstate, just before its terminus, actually veer to the southwest. Vehicles bound for Canada can use northbound I-91 to reach the Derby Line/Stanstead border crossing at that Interstate's end, and
northwards into Canada as an "autoroute" freeway into the Canadian province of
Quebec. The portion of I-93 in Vermont parallels both
U.S. Route 2 and
Vermont Route 18.

History

Southeast Expressway

The Southeast Expressway was constructed between 1954 and 1959, at the same time the
John F. Fitzgerald Expressway (Central Artery) was built. Its northern terminus is at Exit 18 (Massachusetts Avenue) in South Boston, a former Y-interchange where the cancelled
Inner Belt (I-695) was to meet with the expressway and the Central Artery. The southern terminus is at the Y-interchange (the "
Braintree Split") at Exit 7 in Braintree (the former southern terminus of
Route 128). A section of the Expressway, beginning south of the Savin Hill overpass and ending just before the Braintree Split utilizes a
zipper lane, in which a movable barrier carves out a reversible
high occupancy vehicle lane on the non-peak side of the highway during
rush hour. Most of the right of way for the
Granite Railway in
Milton and
Quincy was incorporated into the expressway.[13]

The Central Artery, officially the
John F. Fitzgerald Expressway, was a section of highway in downtown Boston constructed in the 1950s and was originally designed as a fully elevated highway. This new highway was greatly disliked by the citizens of the city because it cut the heart of the city in half, cast long, dreary shadows and was an eyesore to the community. Because of the public outcry, Gov.
John Volpe ordered the southern half of the highway redesigned so that it was underground; this section became known as the
Dewey Square Tunnel. With the cancellation of the highway projects leading into the city in 1972 by Gov.
Francis W. Sargent, the Central Artery gained the designation of Interstate 93 in 1974. It has also carried the local highway designations of
U.S. 1 (since 1989) and
Route 3.

By the mid-1970s, I-93 had outgrown its capacity and had begun to deteriorate due a lack of maintenance. State Transportation Secretary
Frederick P. Salvucci, aware of the issues surrounding the elevated roadway, proposed a plan conceived in the early 1970s by the
Boston Transportation Planning Review to replace the rusting elevated six-lane Central Artery with a new, more efficient underground roadway. This plan was merged with a long-standing proposal to build a third harbor tunnel to alleviate congestion in the
Sumner and
Callahan tunnels to
East Boston; the new plan became known as the Central Artery/Tunnel Project or the Big Dig.

These new roadways were built during a twelve-year period from 1994 to early 2006. The massive project became the largest urban construction project ever undertaken in American history.[14] Construction on the new I-93 segment was not without serious issues: a lengthy Federal environmental review pushed the start of construction back from approximately 1990, causing many inflationary increases; funding for the project was the subject of several political battles between Pres.
Ronald Reagan and Rep.
Thomas P. O'Neill, Jr. Major construction on the new roadway was done while maintaining the old roadway, a step that also greatly increased the cost of the project. The original
Charles River crossing, named Scheme Z, was the object to great public outcry similar to that of the building of the original highway. The outcry eventually led to the replacement of Scheme Z with a newer, more sleek
cable-stayed bridge and complementing exit for
Cambridge, increasing the cost even more.

In Downtown Boston, I-93 is now made up of the
Thomas P. O'Neill Jr. Tunnel and the
Zakim Bunker Hill Bridge, which spans the Charles River. The underground construction of the tunnel system was completed as of October 2006; however, repairs continue to many parts of the tunnel due to water leakage because of improper construction of the
slurry walls supporting the O'Neill tunnel. The former route of the above-ground Artery, so named "the other
Green Monster" by Mayor
Thomas Menino, was replaced mostly by open space known formally as the
Rose Kennedy Greenway.

Additional improvements were done in the
South Bay section of the highway: The I-90/I-93 interchange was completely redesigned, a new
HOV lane extending from the zipper lane in Quincy was added and the South Boston Haul road that was constructed to bypass truck traffic around residential streets in the South End is now open to general traffic.

Hazardous cargoes are now prohibited from I-93 in Boston due to safety issues in the tunnels; these cargoes must now exit at either the
Leverett Circle connector in Cambridge when traveling southbound or at the Massachusetts Ave. exit when traveling northbound.

Northern Expressway

The Northern Expressway was constructed from
Medford to the New Hampshire border between 1956 and 1963. It was extended through
Somerville and
Charlestown to the
Central Artery,
U.S. Route 1, and the planned route of the
Inner Belt between 1965 and 1973. Because it was already under construction, the highway was granted an exception to the moratorium on highway expansion inside Route 128 which was announced in 1970.[15]

I-93's original southern terminus was in Cambridge (just north of Boston) where it was to meet the Inner Belt (I-695). However, when that route was canceled, and the I-95 section into Boston was canceled and rerouted along
Route 128 in the mid-1970s, I-93's route was extended an additional 18 miles (29 km) down the Central Artery (which had been signed as a concurrency of I-95/MA-3 before I-95 was rerouted) and the
Southeast Expressway (what was then just
Route 3) from Boston to
Braintree and then west along former Route 128 to its intersection with I-95 in Canton.

In an attempt to alleviate rush-hour traffic jams, travel in the
breakdown lane of I-93 is permitted on a small stretch between Exit 41 and Exit 47/48. This extra travel is permitted on the southbound side on weekdays between 6AM and 10AM, and on the northbound side between 3PM and 7PM. However, on most busy days this fails to prevent traffic delays. The Massachusetts State Police is displeased with this arrangement, citing that traffic in the breakdown lanes interferes with the ability of emergency vehicles to respond to accidents.

Rapid bridge replacement project

In August 2010, in
Medford, a 25-by-7-foot (7.6 m × 2.1 m) section of bridge deck on the northbound side partially collapsed due to age-related structural fatigue.[16] The collapse forced the
Massachusetts Department of Transportation to evaluate the remaining bridges along the corridor, eventually deciding to replace several bridges along the highway in a plan called 93 Fast 14. MassDOT set in motion a plan to replace the superstructure and concrete decks on 14 overpass bridges along that section of the interstate, using
rapid bridge replacement methods. The $98.1 million project replaced bridges originally built in 1957 with a set of prefabricated modular concrete bridges in a series of weekend roadway closures. Traffic was diverted into a series of crossover lanes during construction. The main part of the project took place each weekend from June through August 2011,with the exception of the July 4th holiday weekend. One or two bridges were replaced each weekend during the construction time frame. The project was part of the Commonwealth's Accelerated Bridge Program.[17][18]

Methuen Rotary

Off exit 46 in
Methuen, Massachusetts, the surface level traffic circle is being rebuilt as part of an overall infrastructure improvement that included a new 8-lane bridge for I-93.

New Hampshire

Exit 1 in Salem was originally designed and built with ramps allowing northbound traffic to exit to
Rockingham Park and return drivers to southbound 93 only. The complementary ramps were added much later, with the southbound off ramp being a particularly tight and dangerous turn squeezed within the curve of the southbound on ramp, which was replaced in August 2012.

A 7.6-mile (12 km) section of I-93 through
Franconia Notch State Park, called the Franconia Notch Parkway, was constructed as a
two-lane freeway with a median divider. This was built as a compromise between the state's park department and highway officials. The speed limit on the parkway is 45 mph (70 km/h). Originally, this section's signage read "U.S. 3 TO I-93", complete with its own exit number sequence, but this has since been replaced by I-93 and
US-3 signage along the entire length of the parkway. The exits were renumbered to Exit 34A, 34B, and 34C. This section of the highway is now the only remaining section of two-lane freeway on an Interstate highway in the United States.

Vermont

Construction of Interstate 93 was completed in 1982 in Vermont. It was planned to be built longer if I-91 didn't change its designation eastward in northeastern part of the state.[19] It was the last interstate to be built in the state.[20]

Future expansion

Massachusetts plans

Since 1996, MassHighway has studied rebuilding the intersection of I-93 and I-95 in
Woburn along the border with
Stoneham and
Reading.[21] The project was expected to start in Spring 2017 and cost $267 million, however continued community opposition has postponed the project indefinitely.[22] A project to upgrade the I-93/I-95 interchange in Canton is now underway with the final phase, to construct new flyover ramps that will take traffic from I-95 North over I-93 and from I-93 South to I-95 South, due to start in 2018.[23]

An additional proposal around 2010 to upgrade
MA Route 24, running southwards from I-93's current Exit 4, to
Interstate 195 near
Fall River, MA also has been put off due to studies showing the cost of the project being very high.[24]

The
Massachusetts Department of Transportation and its predecessor
MassHighway have planned on widening I-93 to a uniform four travel lanes in both directions from the current lane drop near Exit 41 in
Wilmington to the New Hampshire border since the beginning of the 2000s.[25] The first section of widening will be done as part of the I-93 Tri-Town Interchange Project. The project will construct a new interchange in Wilmington. I-93 will be widened from 3 to 4 lanes in each direction from Exit 41 to I-495, a distance of approximately 5 miles (8 km), as the first phase in widening I-93 from Exit 41 to the New Hampshire state line. Early estimates of the entire project place the cost at $567 million.[26]

New Hampshire plans

Initial plans to widen I-93 to a uniform four travel lanes in both directions from
Salem to
Manchester beginning in 2008 were put on hold due to a lawsuit designed to force the
NH Department of Transportation to update the plans to include other transportation options. Under orders from US District Court, the NHDOT and
US Department of Transportation must provide an updated environmental review. The
Conservation Law Foundation (CLF) filed a lawsuit in February 2006, hoping to force any expansion plans in the area to include the restoration of commuter rail service between Manchester and Boston.[27] Despite the suit, the Exit 1 interchange construction was allowed to undergo upgrading and expansion; other associated projects related to the widening, chiefly around Exits 3 and 5, were also eventually allowed to proceed. The whole set of projects were eventually allowed to move forward when an agreement between the state and the CLF that removed the group's opposition to construction which does not pose a threat to the environment.[28]

As part of the
2009 stimulus package, New Hampshire was set to receive several million dollars in highway construction funds. One of the projects was the widening of a portion of the highway between the Massachusetts border and Manchester. Bidding was set to begin in February 2009 with construction slated to begin in late 2009 or early 2010.[29] The plans call for the New Hampshire Department of Transportation to widen the southernmost 20 miles (32 km) of I-93 to four lanes in each direction, from the current two. In addition, all five interchanges along this length will be upgraded to accommodate larger amounts of traffic, including replacing many aging bridges. Smaller construction projects at some of the interchanges are already taking place.[28] According to plans filed by the state with US DOT, the project is scheduled to run from 2009 through 2016, with work starting at the Massachusetts line and moving northward to Manchester. The project is designed with an intermodal transit bent; new or improved park and ride facilities deployed at exits 1, 3 and 5 and a widened median strip that is designed to accommodate a planned commuter rail service between Boston and Manchester.[30]

As a way to help defray the costs of the expansion, in early 2010 the NHDOT made a formal request to the
Federal Highway Administration to add tolls to I-93 at the Massachusetts-New Hampshire border. The new toll facility was to be located in Salem, New Hampshire, approximately .5 mi (0.80 km) from the state line, and would cost travelers $2 per car. The proposal faced opposition from state legislators in both states who claimed the tolls would cause severe congestion in the area and lead to an economic burden to local residents. Opponents included US senator
Scott Brown (
R-Massachusetts).[31] The proposal was eventually dropped in favor of issuing new state bonds to pay for expansion. The new policy was laid out by Transportation Commissioner George Campbell after reviewing the proposal and receiving a promise from the
MassDOT that it would not be enacting a similar toll on the Massachusetts side of the border.[32]

Plans were announced in 2012 that I-93 would have a new northbound and southbound bridge over
Interstate 89 in
Bow, New Hampshire. To reduce traffic on the southbound bridge the NHDOT added a third lane to ease congestion. The bridges were completed in 2014.

More plans were announced in 2014 that the
Hooksett, New Hampshirerest areas would be rebuilt. The new rest areas would feature a 14 pump
Irving gas station, a new New Hampshire liquor and wine outlet, and a few restaurants and shops. The project was completed in 2015.

Exit list

Exits 17, 19, 21, and 25 in Massachusetts were eliminated as part of the
Big Dig. Massachusetts exit numbers were to be changed to those based on I-93 mileposts with a project that was due to start in early 2016, but this project has been indefinitely postponed by MassDOT.[33][34]

New partial cloverleaf interchange, with the former Methuen Rotary having been closed and replaced on August 20, 2016. Now signed northbound as exit 46A (eastbound) and exit 46B (westbound). exit 46B opened October 18, 2017.[7])